class Student:
    name: None
    gender: None
    age: int

    def study(self):
        print("学习了")
        print(f"我是：{self.name}")


# 创建对象
stu_1 = Student()
stu_1.name = '张三'
stu_1.gender = '男'
stu_1.age = 15

print(stu_1)
stu_1.study()
